feat(app,learn): shared spaces' members on the device

Step 4 (e) of ADR 0044, its first part, for every app's screens.

- halkyon_app: `SharedSpaceGateway` on the module's `sharedSpace`
  endpoint (the spaces, their members and roles, inviting, handing on,
  leaving), refusals as `SpaceRefused`; `SharedKeys.trustIn` gives
  each member's safety code and whether it was compared or their keys
  changed, `markCompared`, and `trustNewKeys`, which pins the keys
  whose code was compared and never those the instance hands next.
  `FakeSharedSpaceServer` keeps the module's rules for tests, in step
  with `FakeSharedKeysServer`, which now knows members' handles.
- Learn's sharing makes its space through it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/lib/src/feature/sharing/data/studyset_sharing.dart

@@ -1,5 +1,7 @@
 import 'dart:developer';
 
+import 'package:halkyon_app/halkyon_app.dart' show SharedSpaceGateway;
+
 import 'package:halkyon_learn_flutter/src/core/privacy/data/privacy.dart';
 import 'package:halkyon_learn_flutter/src/core/work/work_progress.dart';
 import 'package:halkyon_learn_flutter/src/feature/archive/data/archive_exporter.dart';
@@ -8,7 +10,6 @@ import 'package:halkyon_learn_flutter/src/feature/archive/model/import_archive.d
 import 'package:halkyon_learn_flutter/src/feature/export/data/studyset_markdown.dart'
     show ExportFile;
 import 'package:halkyon_learn_flutter/src/feature/publish/data/publish_gateway.dart';
-import 'package:halkyon_learn_flutter/src/feature/sharing/data/shared_space_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/studyset/data/studyset_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/studyset/data/studyset_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/studyset/model/studyset_tree.dart';
@@ -90,6 +91,9 @@ class StudysetSharing(
   final ArchiveImporter _importer,
   final StudysetDeletions _deletions,
 ) {
+  /// What a Learn space holds, in the module's words for it.
+  static const spaceKind = 'studyset';
+
   static final _stages = WorkStages(
     SharingStage.values,
     weights: const {SharingStage.reading: 2, SharingStage.content: 2},
@@ -116,7 +120,7 @@ class StudysetSharing(
     }
     abort?.check();
 
-    final space = await _spaces.create();
+    final space = await _spaces.create(spaceKind);
     try {
       await _setup.ready(space);
       onProgress?.call(_stages.at(SharingStage.space, done: 1, total: 1));

apps/learn/halkyon_learn_flutter/test/feature/sharing/studyset_sharing_test.dart

@@ -1,4 +1,6 @@
 import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_app/halkyon_app.dart'
+    show SharedSpaceGateway, SpaceInfo, SpaceMember, SpaceRole;
 import 'package:halkyon_app/testing.dart'
     show FakeFileServerGateway, MemoryFileCache;
 import 'package:halkyon_editor/halkyon_editor.dart';
@@ -18,7 +20,6 @@ import 'package:halkyon_learn_flutter/src/feature/learning_path/data/path_progre
 import 'package:halkyon_learn_flutter/src/feature/note/data/note_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_source_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/publish/model/publication.dart';
-import 'package:halkyon_learn_flutter/src/feature/sharing/data/shared_space_gateway.dart';
 import 'package:halkyon_learn_flutter/src/feature/sharing/data/studyset_sharing.dart';
 import 'package:halkyon_learn_flutter/src/feature/study/data/review_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/study/model/rating.dart';
@@ -303,7 +304,8 @@ class _Spaces() implements SharedSpaceGateway {
   final deleted = <String>[];
 
   @override
-  Future<String> create() async {
+  Future<String> create(String kind) async {
+    expect(kind, 'studyset');
     final space = 'space-${made.length + 1}';
     made.add(space);
     return space;
@@ -311,6 +313,32 @@ class _Spaces() implements SharedSpaceGateway {
 
   @override
   Future<void> delete(String space) async => deleted.add(space);
+
+  @override
+  Future<List<SpaceInfo>> mine() => throw UnimplementedError();
+
+  @override
+  Future<List<SpaceMember>> members(String space) => throw UnimplementedError();
+
+  @override
+  Future<SpaceMember> invite(String space, String handle, SpaceRole role) =>
+      throw UnimplementedError();
+
+  @override
+  Future<void> setRole(String space, String member, SpaceRole role) =>
+      throw UnimplementedError();
+
+  @override
+  Future<void> remove(String space, String member) =>
+      throw UnimplementedError();
+
+  @override
+  Future<void> handOn(String space, String member) =>
+      throw UnimplementedError();
+
+  @override
+  Future<void> leave(String space, {String? nextOwner}) =>
+      throw UnimplementedError();
 }
 
 /// The device's side of a new space: the spaces readied and the studysets